5-azaspiro[2.4]heptane-6-carboxylic acid, or 4-spirocyclopropyl proline, and its derivatives have been found to be useful intermediates in the preparation of reagents for the treatment of HCV infection (for example, see: WO2009/102325A1, WO2010/099527A1 and WO2010/132601A1). The preparation of 4-spirocyclopropyl proline derivatives generally involves treatment of a 4-exocyclic methylene-substituted proline compound with a metal carbenoid generated through Simmon-Smith reaction or its different variations (e.g. Et2Zn/ClCH2I, Et2Zn/CH2I2/CF3COOH). The reaction suffers from incomplete conversion and hence low yield and difficult purification. It also frequently requires the use of excess amount of extremely air-sensitive and hightly flammable reagent, Et2Zn, which is difficult to handle and poses a great fire harzard. These current processes are not amenable to large scale synthesis. There is an urgent need for the development of a practical synthetic process for the preparation of 4-spirocyclopropyl proline derivatives.